As if job losses, foreclosures, and the credit crunch weren’t enough to worry about, researchers have raised yet another possible downside of the economic crisis. Merchant ships are sitting idle at ports, potentially accumulating marine organisms that could be carried to other parts of the world when business picks up.

For years, ships that transport organisms on their hulls have likely helped nonnative marine species invade new habitat around the globe, resulting in damage to both ecosystems and economies. Coating the hulls can prevent “biofouling,” but many of these treatments lose their effectiveness on inactive ships. For instance, a 200-meter ship could amass more than 20 metric tons of organisms if left unused for a long period of time, the authors write.

Since the financial crisis hit, cargo throughput has dropped at several major ports, the researchers say. Singapore, Hong Kong, Busan, Long Beach, and Hamburg have seen declines of 13.7 to 27.1 percent between 2008 and 2009, according to data from port companies. Idle ships are lingering around Malaysia, Indonesia, and the Philippines, and anchor times longer than three months have been reported, the team writes in Marine Pollution Bulletin.

Grounded ships may not be cleaned properly before departure because of the expense and long waits for maintenance, the authors say. That could result in an unusually high number of nonnative marine organisms arriving at destination ports when the economy recovers. ❧—Roberta Kwok